Sunday night's successful SpaceX launch marks another extraordinary new milestone in space. It also provides an opportunity to assess the significant advances we've seen in just four years on Florida's Space Coast.

When President Obama came into office, he inherited a human spaceflight program in crisis. The previous Administration's decision to retire the Space Shuttle by 2010 was exacerbated by the lack of a viable follow-on program. In 2009, an independent commission concluded that the program to replace the Shuttle suffered such significant underinvestment and was so behind schedule that the first crewed flight to the International Space Station (ISS) would not occur until more than a year after the ISS was planned to be deorbited into the ocean.

President Obama knew we could to do better, and took bold, swift action to put NASA on a sustainable path and support the growth of Florida's aerospace sector. As a direct result of his policies, we now have a comprehensive, achievable, and historic vision to push the frontiers of what we can do in space. The President's plan extended the life of the International Space Station, fostered international cooperation in space, supported the growth of America's commercial space industry, and invested in taking on our pressing scientific challenges while continuing the nation's commitment to robust human space exploration, science, and aeronautics programs.

Because of President Obama's leadership, we've seen more NASA-related launches over the past four years from Florida's shores than we would have under the previous plan. He reduced the U.S. human spaceflight gap by extending the Space Shuttle Program with two added missions, delaying its retirement until 2011. He completed the construction and extended the life of the ISS through at least 2020. And he sought to harness U.S. entrepreneurship and competitive spirit to develop safe, affordable, and made-in-America vehicles, while creating thousands of jobs as the commercial space industry develops. Four successful SpaceX launches from Florida's coast over the past three years -- two to the ISS -- have demonstrated the promise of robust aerospace activity the President's space policy offers.

We are now on a trajectory to have U.S. astronauts launching on U.S. rockets from Florida soil sooner than we would have under the previous Administration's plan -- and we're on track to send American explorers deeper into the solar system than ever before.

The road to space has always run through Florida, and it always will. That's why President Obama sought to harness the talent and tenacity of Florida's high-tech workforce as an unparalleled national treasure, crucial for building new industries in the years ahead.

* The International Space Station (ISS), continuously inhabited since 2000, is the centerpiece of our human spaceflight program. Its continued operation depends on U.S. cargo launches from the Space Coast. Florida's universities, small businesses, government labs, and industry are engaged in cutting-edge research on the ISS designed to make future spaceflight more efficient, while providing lasting and significant benefits to life on Earth.

* Earlier this summer the first space-bound Orion craft arrived at the Kennedy Space Center (KSC), and is now being readied for its first test flight, scheduled for 2014. The next-generation Orion spacecraft is supporting hundreds of Space Coast jobs and will continue to add workers in the months ahead.

* In March, we crossed a key developmental milestone for the construction of the most powerful rocket in history. It will take humans farther out into the solar system than ever before. This new rocket, the Space Launch System -- the world's biggest booster since the Apollo Program's Saturn V -- will be the backbone of NASA's manned spaceflight program for decades to come, and will be processed, stacked and launched at KSC, supporting thousands of new jobs.

* August of this year marked another decisive milestone in human spaceflight when NASA selected three U.S. companies with Space Coast facilities as the winners of a $1.1 billion competition. These companies represent U.S. innovation at its best, bringing diverse design concepts and business models, innovative techniques, and unique technical strength to Florida, creating hundreds of new Space Coast jobs in the process.

* NASA is now partnering with universities, including UCF and the Florida Institute of Technology, and small businesses in Florida and across the nation to mature new in-space propulsion systems, lightweight propellant tanks, advanced structures and habitats, radiation protection techniques and life-support systems necessary for our nation's astronauts to become deep space explorers.

By investing in American companies, and American ingenuity, the Obama Administration is spurring free market competition to give taxpayers more bang for the buck while enabling NASA to do what it does best -- explore the unknown.

We can't afford to turn back now. The Romney-Ryan budget could lead to some of the deepest percentage cuts to the space program since the end of the Apollo program. It's not just that Congressman Ryan voted against NASA Authorizations in 2008 and 2010, it's that their plan would undermine the bold vision that the President has outlined and a bipartisan Congress has advanced.

Governor Romney and Congressman Ryan offer a stark choice for the Space Coast. The Romney-Ryan budget calls for deep cuts in domestic discretionary spending - cuts that if applied across the board would force a 5 percent cut to NASA's current budget and by 2014 force an almost 20 percent cut to NASA's budget. Under the Romney-Ryan plan, in just 10 years, the account that houses NASA's aeronautics programs would be cut by 25 percent, which could drastically affect the next-gen research at Florida's Embry-Riddle Aeronautical University. In this same timeframe, NASA's space exploration and development programs would be cut by nearly 10 percent.

Besides his budget, Governor Romney has not articulated any new ideas for NASA. His policy announced in September references the progress that President Obama has made in supporting commercial space flight, but offers neither new ideas nor any commitment to NASA's current mission.

In contrast, speaking at the Kennedy Space Center in April 2010, President Obama stated, "I am 100 percent committed to the mission of NASA and its future." And speaking to the NASA team following the successful landing of the Curiosity rover on Mars in August 2012, the President stated, "I'm going to give you guys a personal commitment to protect these critical investments in science and technology." That's the kind of steady leadership NASA, Florida, and the country deserves.

We, the undersigned, believe that President Obama's vision for growing America's leadership in space through investments in U.S. commercial space companies, high-tech research and development, and deep-space exploration capabilities, is critical for Florida's Space Coast and essential for continued U.S. leadership in space.

Dr. Jim Bell, Professor, Arizona State University School of Earth and Space Exploration, and member of the Mars rover science teams